基于工作过程系统化的光网路课程开发探索与实践

针对以高职光网络课程的开发,以工作过程系统化教学设计理论为指导,以企业工程为载体,整合教学内容,以实际工作过程为脉络开展教学过程,实现在教学设计上学习任务和工作任务的一致性,这有助于教学模式的改革与创新,为高校教育教学改革提供有意义的参考。

光通信技术的发展趋势

本文对光通信技术的发展趋势作了简要介绍和论述,并对面临的技术挑战也作了简要评述。

多芯光纤中基于共享风险组的生存性RCSA算法

传统空分复用弹性光网络中仅考虑纤芯频谱资源的无保护分配,缺少对业务生存性的保障。提出了一种基于共享风险组的生存性路由纤芯频谱分配(RCSA)改进算法,该算法基于共享风险纤芯组的设想,在单根多芯光纤中同时分配业务的工作频隙和保护频隙,并基于纤芯间串扰机理引入了业务分配优先度参数,根据优先度选择引起串扰最小的频隙分配方案。仿真结果表明,所提算法可以在保障业务生存性的同时有效减少带宽阻塞率和芯间串扰。

Using CSMA/CD for Ethernet Passive Optical Network (EPON)

Using CSMA/CD for EPON can eliminate the augmentations, such as multi-point control protocol and point-to-point emulation, added to the existing 802.3 architecture due to the incompatibility of PON to Ethernet. Both full-duplex EPON system and half-duplex EPON system using CSMA/CD were proposed. In the full-duplex EPON, CSMA/CD is used as the upstream MAC protocol. In the half-duplex EPON system, both upstream and downstream traffic contend for the optical channel through CSMA/CD protocol. The upstream lightwave redirection and collision detection techniques were given. By the analysis and simulation, the throughput performance of the half-duplex EPON system is proven to be as well as that of the existing high speed half-duplex Ethernet LAN.

WiFi over Fiber Link and Wavelength Assignment Protocol for Internet of Things

A novel Wireless Fidelity (WiFi) over fiber link and a wavelength assignment protocol are proposed to provide sufficient bandwidth and extensive coverage range for the various applications in the Internet of Things (IoT).The performance of the WiFi over fiber-based wireless IoT network is evaluated in terms of error vector magnitude (EVM) and data throughput for both the up and down links between the WiFi central control system and remote radio units (RRUs).The experimental results illustrate the reliability of the fiber transmission of 64 Quadrature Amplitude Modulation (64QAM) WiFi signals by direct analog modulation.In order to efficiently utilize the wavelength resources,we also demonstrated the wavelength assignment protocol by employing optical switching configurations in Central Station (CS) to realize the wavelength switching,and the simulation results indicate the queuing size and the corresponding queue delay for different numbers of available wavelengths.

Performance Analysis of WLAN Medium Access Control Protocols in Simulcast Radio-Over-Fiber-Based Distributed Antenna Systems

The performance of three wireless local-area network(WLAN) media access control(MAC) protocols is investigated and compared in the context of simulcast radioover-fiber-based distributed antenna systems(RoF-DASs) where multiple remote antenna units(RAUs) are connected to one access point(AP) with different-length fiber links.The three WLAN MAC protocols under investigation are distributed coordination function(DCF) in basic access mode,DCF in request/clear to send(RTS/CTS) exchange mode,and point coordination function(PCF).In the analysis,the inter-RAU hidden nodes problems and fiber-length difference effect are both taken into account.Results show that adaptive PCF mechanism has better throughput performances than the other two DCF modes,especially when the inserted fiber length is short.

Design and Simulation of Routing-switching Protocol Based on Optical Switch Array

An optical routing-switching technology based on optical switch array is proposed.The characteristics of the blocking and nonblocking networks are analyzed and compared,odd-even sorting network is used to realize optical routing-switching,relative routing-switching protocol is designed.Simulation test under load shows that it can reduce a blocking effectively and enhance an efficiency of switching.Further,it can transfer the processing and switching within parallel computer from electric domain to optical domain. It can make parallel computer coordinating computing and processing at much more higher speed, storing and transmitting even more efficiently.

A SYNTHETIC ALGORITHM FOR WAVELENGTH ROUTING IN OPTICAL NETWORK

After analyzing the merits and shortcomings of Fixed-Alternated Routing algorithm (FAR) and Least Loaded Routing algorithm (LLR),we propose one novel dynamic optical routing algorithm. Having considered the influences of path’s length and path’s congestion just like in FAR and LLR,we take into account the network resource status-amount of free wavelengths in the network. Proposed algorithm sets up connections on three possible paths according to amount of available free wave-lengths in the network,which effectively decreases the blocking probability. The National Science Foundation (NSF) network and mesh-torus network simulation results show that the performance of this algorithm is better than that of FAR and LLR.

STUDY ON STRATEGY OF DYNAMIC JOINT ROUTING AND RESOURCE ALLOCATION IN LAYERED OPTICAL TRANSPORT NETWORKS

A layered network model for optical transport networks is proposed in this paper,which involves Internet Protocol(IP) ,Synchronous Digital Hierarchy(SDH) and Wavelength Division Mul-tiplexing(WDM) layers. The strategy of Dynamic Joint Routing and Resource Allocation(DJRRA) and its algorithm description are also presented for the proposed layered network model. DJRRA op-timizes the bandwidth usage of interface links between different layers and the logic links inside all layers. The simulation results show that DJRRA can reduce the blocking probability and increase network throughput effectively,which is in contrast to the classical separate sequential routing and resource allocation solutions.

Wavelength Routing Algorithmof All Optical Network Based on Traffic Engineering

General multi-protocol label switching(GMPLS) based on traffic engineering is one of the possible methods to implement all-optical network. This method implements the network with IP technique and guarantees the quality of service with traffic engineering. Based on the establishment of selecting schemes of optical path and methods of traffic calculation, the wavelength routing algorithm of all-optical network based on traffic engineering is presented by combining with prior route of shortest path and traffic engineering, the algorithm procedures are given, and the actual examples are introduced as well as the analysis on simulation calculation. This research results have certain significance for the achievement of optical switching technique of all-optical network.

Inter-domain routing and wavelength assignment based on source routing in ASON

The inter-domain and intra-domain routings are treated jointly with dynamically distributed algorithms in automatically switched optical networks （ASON） based on source routing. The proposed algorithms are discussed through numerical calculations. The routing loops can be avoided efficiently and the inter-domain signaling complexity is reduced significantly. The performance of the blocking probability is also improved.

QoT-Aware Grooming, Routing, and Wavelength Assignment(GRWA) for Mixed-Line-Rate Translucent Optical Networks

A Mixed Line Rate(MLR)optical network is a good candidate for a core backbone network because of its ability to provide diverse line rates to effectively accommodate traffic demands with heterogeneous bandwidth requirements.Because of the deleterious effects of physical impairments,there is a maximum transmission reach for optical signals before they have to be regenerated.Being expensive devices,regenerators are expected to be sparsely located and used in such a network,called a translucent optical network.In this paper,we consider the Grooming,Routing,and Wavelength Assignment(GRWA)problem so that the Quality of Transmission(QoT)for connections is satisfied,and the network-level performance metric of blocking probability is minimized.Cross-layer heuristics to effectively allocate the sparse regenerators in MLR networks are developed,and extensive simulation results are presented to demonstrate their effectiveness.

Joint routing and resource allocation in optical transport networks

A layered network model for optical transport networks is proposed in this paper,which involves IP,SDH and WDM layers.The strategy of Dynamic Joint Routing and Resource Allocation (DJRRA) and its algorithm description are also presented for the proposed layered network model.DJRRA optimizes the bandwidth usage of interface links between different layers and the logic links inside all layers.The simulation results show that in contrast to the classical separate sequential routing and resource allocation solutions,DJRRA can reduce the blocking probability and increase network throughput effectively.

ROUTING AND WAVELENGTH ASSIGNMENT ALGORITHMS BASED ON EQUIVALENT NETWORKS

In this paper, a Wavelength Division Multiplexing (WDM) network model based on the equivalent networks is described, and wavelength-dependent equivalent arc, equivalent networks, equivalent multicast tree and some other terms are presented. Based on this model and relevant Routing and Wavelength Assign- ment (RWA) strategy, a unicast RWA algorithm and a multicast RWA algorithm are presented. The wave- length-dependent equivalent arc expresses the schedule of local RWA and the equivalent network expresses the whole topology of WDM optical networks, so the two algorithms are of the flexibility in RWA and the optimi- zation of the whole problem. The theoretic analysis and simulation results show the two algorithms are of the stronger capability and the lower complexity than the other existing algorithms for RWA problem, and the complexity of the two algorithms are only related to the scale of the equivalent networks. Finally, we prove the two algorithms’ feasibility and the one-by-one corresponding relation between the equivalent multicast tree and original multicast tree, and point out the superiorities and drawbacks of the two algorithms respectively.

High-Speed Road Measurement Systems： Integration of Pavement and General Mapping Laser Technologies

Performing surveys on a single section of a road is quite different from that on a road network. In the first case, the need for performance characteristics of the pavement may be of service to rehabilitation. Surveying a road network, instead, aims to establish service levels, identify deficiencies and priorities and define budgets for maintenance. This challenge needs a methodological approach in order to widen the action plan and optimize the cost-benefit analysis of each asset through the use of preventive maintenance policies. High-speed monitoring systems on the market were specialized towards the necessity of measuring specific performance of the pavement or mapping land （data inventory）. The technological development of instrumentations such as inertial systems and synchronizers has enabled the integration of different devices and the achievement of the best correlation of data. This is the case of the LARAN （laser road analyzer）, whose helpfulness will be presented within a case study in which geometrical data and surface characteristic information-cracks, texture, profiles-were obtained through a unique survey. The cross-analysis resulted efficient for safety purposes and also for the identification of “black points” corresponding to boundary operative conditions of the road with respect to technical standards and recommendations.

Transmission Mechanism Based on Burst Filling in Hybrid Optical Burst/Circuit Switching Networks

Hybrid optical switching networks make full use of the advantages of Optical Circuit Switching(OCS)and Optical Burst Switching(OBS).In parallel hybrid optical switching networks,edge nodes choose a switching mode for traffic and no longer change.The inflexible decision making of the traffic transfer mode leads to low resource utilization when the arrival rate of the OCS traffic is lower than the capacity of the light path.In this paper,a new transmission scheme is proposed to improve resource utilization for hybrid optical switching networks.When the traffic arrival rate of the light path is lower than the transmission rate of the light path,the OCS traffic flow is reshaped at the edge nodes to generate a series of voids.Then,several message packets are sent along the light path to inform the core nodes of the voids of the light paths that represent the unused bandwidth resources.To improve the resource utilization,the voids can be filled with data bursts by core nodes.The simulation results show that the new scheme can effectively reduce the burst loss rate and improve the link utilization of the hybrid optical switching network on the premise of a providing service quality guarantee for OCS traffic.

Re-modulated technology of WDM-PON employing different DQPSK downstream signals

This paper proposes a kind of modulation architecture for wavelength-division-multiplexing passive optical network （WDM- PON） employing optical differentia/quadrature phase shift keying （DQPSK） downstream signals and two different modulation formats of re-modulated upstream signals. At the optical line terminal （OLT）, 10 Gbit/s signal is modulated with DQPSK. At the optical network unit （ONU）, part of the downstream signal is re-modulated with on-offkeying （0OK） or inverse-return-to-zero （IRZ）. Simulation results show the impact on the system employing NRZ, RZ and carrier-suppressed return-to-zero （CSRZ）. The analyses also reflect that the architecture can restrain chromatic dispersion and channel crosstalk, which makes it the best architecture of access network in the future.

Study of dual-polarization OQAM-OFDM PON with direct detection

An offset quadrature amplitude modulation orthogonal frequency-division multiplexing(OQAM-OFDM) passive optical network(PON) architecture with direct detection is brought up to increase the transmission range and improve the system performance.In optical line terminal(OLT),OQAM-OFDM signals at 40 Gbit/s are transmitted as downstream.At each optical network unit(ONU),the optical OQAM-OFDM signal is demodulated with direct detection.The results show that the transmission distance can exceed 20 km with negligible penalty under the experimental conditions.